For measuring the angle of tilt of a lens-mounting rim, i.e. the angle by which a single lens-mounting rim is tilted with respect to a horizontal tangent to the center of the bridge of a spectacles frame, no means of measurement have yet become known which would be suitable for measuring this specific angle. Measurement means described in the technical literature exclusively serve for measuring a bending of a frame.
A paper by Johannes Eber, entitled “Anatomische Brillenanpassung” (Anatomic Fitting of Spectacles), published by “Optische Fachveroeffentlichungen GmbH”, Heidelberg, 1987, describes that a spectacles frame fitted with large lenses will be bent to a certain extent. This paper merely discusses the way of fitting the spectacles frame, but not the effect of the bending on the optical properties of the spectacles lenses.